The invention relates to an arrangement for open-end friction spinning with two adjacently arranged rollers driven in the same rotational direction and forming a wedge-shaped gap which serves as yarn formation region, the rollers each including a perforated shell. Each shell contains a suction insert having a suction slot facing in the direction of the wedge-shaped gap and extending essentially in longitudinal direction to the gap. A fiber feeding device is provided containing a fiber feed channel which feeds single fibers into a dispersion zone along the wedge-shaped gap. Further, a yarn withdrawal device is included which withdraws the producing yarn in longitudinal direction of the wedge-shaped gap out of the dispersion zone and subsequently through a connecting treatment zone of the wedge-shaped gap. Further, a housing means is included covering the rollers in the area of the wedge-shaped gap. Arranged in the housing, the mouth of the fiber feed channel and an air inlet opening extend essentially in the longitudinal direction of the wedge-shaped gap.
With a known arrangement of the above-mentioned type such as disclosed in U.S. Pat. No. 4,483,136, the air inlet opening is coordinated to the roller rotating out of the wedge-shaped gap. An air stream is created through this air inlet opening which has the purpose to loosen the fibers which eventually are carried with the roller rotating outwardly from the yarn formation region. The air inlet opening extends beyond the area of the dispersion zone such that an air stream is produced which is directed into the wedge-shaped gap in the area of the treatment zone as it serves to hold the yarn in the gap. In this construction, the suction slots of the suction inserts as well as the air inlet opening exhibit a constant cross-section in the longitudinal direction of the yarn. With such an arrangement, it is difficult to proportion the spinning conditions and especially the friction effect in the area of the dispersion zone and the treatment zone.
It is also disclosed in commonly assigned U.S. application Ser. No. 694,779, filed Jan. 25, 1985, now U.S. Pat. No. 4,606,1887, to vary the suction effect along the length of the wedge-shaped gap.
It is an object of the present invention to provide an arrangement which provides for proportioning the spinning condition and especially the friction effect in the area of the dispersion zone and the treatment zone.
It is a further object according to certain preferred embodiments to provide an arrangement which proportions the suction conditions in the area of the dispersion zone and the treatment zone.
The objects are achieved in accordance with the invention by providing that the two suction slots of the two suction inserts are of a total cross-section that is changeable in longitudinal direction of the wedge-shaped gap, and that the air inlet opening essentially corresponds in size to the changing total cross-section of the suction slots in the longitudinal direction of the wedge-shaped gap.
The proportioning of the airstreams is accomplished by the arrangement of total cross-section of the suction slots of both suction inserts in connection with the size of the air inlet opening. The airstreams constitute an important aspect with regard to the friction effect in the wedge-shaped gap. It is thereby also possible to proportion the friction effect in the yarn withdrawal direction for obtaining optimum spinning results.
In a further development of certain preferred embodiments of the invention, it is provided that the suction slots of the suction inserts exhibit different lengths in longitudinal direction of the wedge-shaped gap. In this arrangement, it is possible to proportion the suction effect in a simple manner by retaining the same width of the suction slots.
In a further development of certain preferred embodiments of the invention, it is provided to adjust the size of the inlet air opening by means of an adjusting device. It is thereby made possible to accommodate spinning conditions with changing fiber materials and/or different yarn numbers.
In a still further development of the invention, it is provided that the cover is formed by a housing element surrounding the rollers at least in the area of the dispersion zone and the treatment zone to create a housing therefor. In this arrangement exactly defined airstreams are present in the area of the dispersion and the treatment zones which are not affected by any outside air flow. The airstreams are determined by the size of the air inlet opening and the size and length of the opening of the fiber feed channel.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, several embodiment in accordance with the present invention.